The idea of busking "auditions" seems pretty ridiculous to me, unless the only type of busking to be tolerated is that of musicians with a high degree of technical skill. I would certainly fail that sort of audition, although I have been able to pull crowds, hold them and entertain them over twenty five years. I wonder how many of those, who pass the audition will be able to do that?
The best way to find out is to either ask the local buskers or drop in at the town hall. Busking is rarely completely legal, but it is often tolerated if the buskers are polite and tactful.